Functionalization of colloidal quantum dots (QDs) with chiral cysteine derivatives by phase-transfer ligand exchange proved to be a simple yet powerful method for the synthesis of chiral, optically active QDs regardless of their size and chemical composition. Here, we present induction of chirality in CdSe by thiol-free chiral carboxylic acid capping ligands (l- and d-malic and tartaric acids). Our circular dichroism (CD) and infrared experimental data showed how the presence of a chiral carboxylic acid capping ligand on the surface of CdSe QDs was necessary but not sufficient for the induction of optical activity in QDs. A chiral bis-carboxylic acid capping ligand needed to have three oxygen-donor groups during the phase-transfer ligand exchange to successfully induce chirality in CdSe. Intrinsic chirality of CdSe nanocrystals was not observed as evidenced by transmission electron microscopy and reverse phase-transfer ligand exchange with achiral 1-dodecanethiol. Density functional theory geometry optimizations and CD spectra simulations suggest an explanation for these observations. The tridentate binding via three oxygen-donor groups had an energetic preference for one of the two possible binding orientations on the QD (111) surface, leading to the CD signal. By contrast, bidentate binding was nearly equienergetic, leading to cancellation of approximately oppositely signed corresponding CD signals. The resulting induced CD of CdSe functionalized with chiral carboxylic acid capping ligands was the result of hybridization of the (achiral) QD and (chiral) ligand electronic states controlled by the ligand's absolute configuration and the ligand's geometrical arrangement on the QD surface.

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In an effort to design deep-blue light emitting materials, the optical and electronic properties of a series of tetraarylbenzobis[1,2-d:4,5-d’]oxazole (BBO) cruciforms were evaluated using density functional theory (DFT) and time-dependent...

For the supramolecular chemistry of self-assembly systems, a major goal is to achieve the level of control of the assembly process equal to the capabilities of classical asymmetric organic synthesis, such as high stereospecificity, regiospecificity, and reproducibility. Herein we report the stereoselective porphyrin-driven formation of left- and right-handed, chiral functional supramolecular nanoassemblies with mirror image chiroptical properties templated by a single homochiral ssDNA by changing the cooling rate, DMSO, and salt concentration. Upon dialysis and annealing that caused the porphyrin units to relax into their preferred slipped cofacial stacking geometry, the nanoassemblies displayed near ideal mirror-image chiroptical properties, as well as unusually high thermal and acid–base structural stability. ssDNA–porphyrin nanoassemblies preserved their photocatalytic activity in the visible spectral range as demonstrated by iodide oxidation. ssDNA–porphyrin nanoassemblies formed higher order fluorescent nano- and microstructures as evidenced by TEM and confocal microscopy. We propose a plausible mechanism for the formation of nanoassemblies and induction of helicity based on our molecular dynamics (MD) simulations, time-dependent density functional theory (TD DFT) computations, and experimental spectroscopic data. We suggest that the ssDNA templates interact with preformed achiral porphyrin columnar nanostacks. These results provide further insight into the stereoselective synthesis of chiroptical nanostructures and control of supramolecular helicity.

We studied CdS QDs capped with chiral epimers, structural analogs, and positional isomers and determined that match/mismatch stereo-effects together with position and type of functional group affect the optical and chiroptical properties of CdS.